2025/12/26 by Koki Numa, Eri Matsuda, Numa, Koki +5
Materials Science · Physics and Astronomy · #FOS: Physical sciences #Iron-based superconductors research #Physics of Superconductivity and Magnetism #Rare-earth and actinide compounds #Strongly Correlated Electrons (cond-mat.str-el)
paper · doi:10.48550/arxiv.2512.21931
openalex publication_date 2025/12/26 · openalex created_date 2025/12/30 · openalex updated_date 2026/07/28
The heavy-fermion superconductor CeRh2As2 exhibits a non-superconducting phase transition that precedes the emergence of superconductivity. The nature of the corresponding order parameter remains under debate, with competing proposals involving magnetic dipoles or electric quadrupoles. We derive the momentum-dependent multipolar susceptibilities and effective interactions among the localized 4f electrons, based on the framework of density functional theory combined with dynamical mean-field theory. Magnetic fluctuations within the crystalline-electric-field (CEF) ground-state doublet are dominated by q=(1/2,1/2,0), corresponding to a two-dimensional checkerboard configuration of the magnetic moment Mz along the c axis. Hybridization between the CEF ground-state and the first-excited doublet gives rise to leading magnetic octupole fluctuations of z(x2-y2) symmetry, followed by electric quadrupole fluctuations of x2-y2 and yz, zx symmetries. By taking into account the anisotropic magnetic-field dependence of the transition temperature T0, we conclude that an antiferromagnetic order of Mz at q=(1/2,1/2,0) is consistent with the experiments, owing to the enhancement of T0 caused by fluctuations of the field-induced quadrupole of yz, zx type under an in-plane magnetic field.